Bisphenol A induces endoplasmic reticulum stress-associated apoptosis in mouse non-parenchymal hepatocytes

Aims: the effects of bisphenol A (BPA) on NCTC Clone 1469, non-parenchymal hepatocytes, were examined to clarify the molecular basis of BPA-induced liver injury.

Main methods: we analyzed the expression of C/EBP homologous protein (CHOP) mRNA, Bcl2 mRNA, caspase12, and glucose-regulated protein 78 kDa (GRP78)/Ig heavy chain-binding protein (BiP), to determine whether endoplasmic reticulum (ER) stress was involved in the 100 μM BPA-induced cell death. To examine the features of damaged hepatocytes, we analyzed the morphological changes in BPA-treated NCTC Clone 1469 by transmission electron microscopy. In addition, we analyzed the intracellular reactive oxygen species (ROS) level in BPA-treated NCTC Clone 1469 by the 2', 7'-dichlorofluorescein diacetate (DCFDA) method.

Key findings: increases in the expression of CHOP mRNA, caspase-12, and GRP78/BiP in NCTC Clone 1469-treated with 100 μM BPA were detected (CHOP, 1.42 fold; caspase-12, 1.33 fold; GRP78/Bip, 1.36 fold). These observations suggested that BPA induced ER stress-associated apoptosis. A morphological analysis revealed remarkable elongation of the rough ER, supporting the finding of ER stress. Intracellular ROS production was increased in NCTC Clone 1469-treated with BPA, and N-acetyl-l-cysteine (NAC) prevented the cell damage induced by BPA. However, these effects of BPA were not inhibited by estrogen receptor inhibitors.

Significance: we found that BPA induced ER stress-associated apoptosis in non-parenchymal hepatocytes. The ER stress is due to ROS production and is independent of estrogen receptors.